Droplet model

from Wikipedia, the free encyclopedia

The drop model describes an atomic nucleus as a liquid drop . George Gamow developed the basic idea . In 1935 Carl Friedrich von Weizsäcker presented his Bethe-Weizsäcker mass formula based on it (further developed by Hans Bethe ) for atomic nuclei, which agrees well with the observed masses. In 1936, Niels Bohr further developed the droplet model ( compound nuclear reaction as a possible mechanism of nuclear reactions ). Lise Meitner and Otto Frisch used the droplet model in 1939 for the first explanation of nuclear fission and the nuclear energy released in the process . John Archibald Wheeler (with Niels Bohr, as a model for nuclear fission) and Enrico Fermi made further contributions.

The droplet model describes the binding energies of the nuclei in good agreement with the measured values . The basic assumption here is that there is a strong attractive nuclear force between the components of a nucleus ( nucleons , i.e. protons and neutrons ) , but this has such a short range that it only acts between directly neighboring nucleons. This means that the mass density in all atomic nuclei is largely the same, similar to that of water droplets formed from water molecules, only that the density of the nuclei is 10-14 times that of water.

The mutual electrical repulsion of the protons, the Coulomb force , is weaker than the attractive nuclear force even between neighboring protons, but it has a long range and therefore covers all other protons of a nucleus from one proton. Therefore, the more protons they contain, the less stable they are. Nuclei that contain more than 82 protons are unstable, i.e. radioactive . Since nuclei with 43 and 61 protons are also unstable due to the precise conditions, there are exactly 80 different stable chemical elements . Another 13 radioactive elements occur naturally on Earth because of their long half-life , with the maximum number of protons being 94.

The droplet model also gave rise to mathematical research.

Web links

Individual evidence

  1. George Gamow: Mass defect curve and nuclear constitution, Proc. Roy. Soc. A, Volume 126, 1930, pp. 632-644
  2. Rustum Choksi et al. a .: An Old Problem Resurfaces Nonlocally: Gamow's Liquid Drops Inspire Today's Research and Applications, Notices AMS, 2017, No. 11, Online